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Locost: A long due update

I have five unfinished articles sat in my inbox. Half technical, half updates. But I haven’t been able to bring myself to finish any of them. Free time to write is hard to come by these days, and I am very picky about what I choose to publish. However, it has been far too long without an update, and I owe you all some words and pictures. So here goes.

Dyno

This time last year I was gearing up for a trip to the dyno. I was going to get the car tuned and then head over to Castle Combe for a cold/wet trackday to round the year off.

My main motivation for putting the car on the rollers was that it hadn’t been running right. I knew something needing adjusting but I just couldn’t put my finger on it. So I decided to put it in the hands of a professional and get it sorted.

On paper, it went badly. Once loaded up on the dyno the car started coughing and wouldn’t run right. After checking a number of things Steve, the resident car doctor, decided to check the compression; just in case. Low and behold, low compression on cylinders #3 and #4. I was kicking myself for having not checked this moons ago, but I was also happy to have found out why the car wasn’t running right. I loaded her back on the trailer and took her home, happy in the knowledge that I would be able to fix the engine back to full health.

The Locost on the Dyno

Tear Down

I took the top-end off of the engine and checked the head and block for straightness. They were both at the top end of suzuki’s specification, especially between cylinders #3 and #4 (0.05mm), and after much pondering I decided to pull the engine to get both the head and blocked skimmed.

Locost Engine Mid Stripdown

Cylinder Head in need of “reflattening”

You can’t even see the dip, but it is thereWith the engine out and the head off I also thought it would also be a good time to check the bearings. They plasti-gauged fine but the surfaces were ruined. Too many years driving with a terrible sump design.

Given that the engine needed a full rebuild and the car was mostly stripped down during Christmas 2018 I had a lot to think about…

The Road to the Road

The car was the most apart it had been since I had first got it moving back in 2012 (was it really that long ago?!?). With life having changed so much in the last few years, the prospect of doing track-days looks less and less appealing. I want to be able to drive the car more often and share it with others.

I decided it was finally time to take the plunge and turn my little red race car into a road car. This was going to be no trivial task. The rule book (IVA Manual) is substantial and requires a large list of tests to be passed for the car to be road registered.

Worst book ever.

I knew there were a number of things that were going to need to be changed and a number of pieces of damaged structure and aesthetic that were going to have to be fixed. But, I am a stubborn old (youngish) fool who is always up for a big project.

I printed out a physical copy of the IVA Manual and marked down every element that needed to be changed, checked or installed. The to-do list is incredibly long, and it doesn’t even cover all the improvements I want to do to the car while it is stripped down. I knew it was going to take well over a year, maybe even two, to complete. But again: I am stubborn fool.

An example of some chassis damage. This rear floor was a moisture trap! Now replaced with a bolt on piece that is easy to clean.

Re-wiring

In my own opinion the original wiring loom was terrible. I continue to point out to people that I was learning to build a car while building this car; it shows. Knowing that I was going to have to install front and rear lights I decided that this was a good time to completely re-wire. All the old loom was stripped out, the old mountings cut out and an entirely blank canvas of aluminium  sheet mounted under the scuttle to attach things too.

New Under Dash

This also ticked off a number of IVA requirements. The loom cannot be accessible under the dash for “radius” reasons, so panelling in underneath was a good idea. It also looks nicer.

In all I managed to entirely re-wire the engine, wire in all the lights (including side repeaters etc) and make use of a set of Ford Puma driver controls including steering lock. I am very happy with the final result. Sadly I have no up to date pictures! These will have to suffice.

The old loom. Oh dear. And out of focus as well.

New fusebox and under dash routing

One from the archives. Shows how much neater the wiring is now!

Lights

As mentioned, the car was going to need appropriately placed front and rear lights. These needed mounting correctly, so I had to buy new rear arches and fabricate front light mounts.

Front Lights and Indicators

New Rear Lights including Number Plate

3D Printed Light Mounts

And The Rest

I have been squirrelling away completing the rest of the rear loom, re-making fuel lines, cleaning up the tunnel, welding in new loom mounts, creating a custom handbrake system, completely replacing the rear diff mount and, just today, welding in the mounts for the mirrors.

The to-do list is still substantial and honestly I think I have another year to go. It will be the tale end of 2020 before I can think about putting this thing in front of the DVLA.

I still have an engine to rebuild and get running again, but I won’ tackle that until everything is done on the chassis and it is stripped down ready to receive said engine. One thing at a time and it’ll be on the road soon enough!

 

 

3D Printing: Improved Inlet Trumpets

Nothing quite gets the internet clickidy-clicks like a 3D printing article! In the following post I use 3D printing to fix something that wasn’t really broken.

The OLD Design

I have never been happy with the original mountings for the inlet trumpets on the Locost. Its quite common to use silicone hose to align everything within a retro-fit throttle body system and sadly mine was no different. This design can lead to miss-alignment between the trumpets and the throttles, potential shrouding of the inlet path and variations in inlet length; cylinder to cylinder.

This is the kind of stuff that keeps me up at night and it needed to be improved.

The original setup used a nice carbon fiber backing  plate to mount the airfilter too. This was as soft as a chocolate tea pot, and four aluminum trumpets were glued-in with black polyurethane sealant. It never failed, it was light and did its job okay; but it wasn’t perfect.

I wanted a new design that would allow me to interchange different length trumpets, for testing on the dyno, and ensure the trumpets would inline with the inlet tract. So I turned to CAD to see what I could conjure up…

The NEW Design

Engine tuning is highly sensitive to inlet path length (read one of the best articles in the world if you want to know more), and I wanted to ensure that this variable remained static/constant. This being the case, It was important that the aluminium inlet trumpets were held up tight to the throttle bodies and positioned concentrically.

I started by measuring the GSXR throttle bodies that currently sit on the engine and then 3D printed some prototypes. The first design to nail down was the backing plate mounts. These would make the transition from the round throttle bodied to the flat air filter backing plate and essentially hold the whole lot to the engine.

I settled on a design that pushed onto the throttle bodies and over a useful cast-in ridge. This then clamped down with a jubilee clip. As a rule of thumb, jubilee clips aren’t super sexy, but when combined with dark grey plastic parts they can look utilitarian and purposeful.

I did try a version that held on using the friction supplied by an M4 bolts. This was a terrible idea. Plastic parts are not strong in tension and it would simply bend the mount when being tightened down.

The final design looked like this.

From here I had a nice flat surface to work. I carried across the jubilee clip compression-based design over to the trumpet side, as it worked so well on the throttle body side. This also allows quick release of the trumpets for switching to different lengths.

Its hard to see in the following CAD drawing, but the whole lot is sealed together with rubber nitrile o-rings. There is an o-ring between the backing plate and the throttle body mount, and an o-ring between the throttle body mount and the throttle body itself. These are super easy to design in, reusable and reliable.

 

Then is was simply a case of printing out eight the separate parts and cutting out the backing plate. The inner prints took approximately 3hrs each to make and the outer 2hrs each.

As always, hit go and come back later. These were made is standard PLA and, as they are on the cold side of the engine, I have no qualms about it.

The whole lot was finished off with some pretty aluminium mounting bolts for the air filter.

This setup is definitely heavier than the previous, but its far more stout and should allow for some fun experimentation on the dyno.

 

 

 

Locost: Baffled and Gated Sump

This is the first part in a series I like to call “What’s wrong with the Locost?” or WWWTL for short. I promised myself I would do a Trackday this year and as things are starting to slow down for the summer I now have time to prepare the car.

Firstly, the Locost is not perfect; I can easily stand and point my finger at a million things “wrong” with it and there are a few things I can’t really live with that I feel I need to amend before it starts turning laps.

You see, as you fix the fundamental setup issues on your home built race car, and attach a set of half decent sticky tyres, you’ll start to go around corners much faster. This has a big effect on the longevity of the car, increasing the loads through the suspension and engine, and you will definitely find some design flaws if you are lucky enough to have any. If you applied good engineering when designing/building said race car you will hopefully have no issues. You would have considered all loading conditions, and you will suffer no tears/breakdowns/failures.

Something I feel I did not consider enough many moons ago, and potentially completely overlooked, was oil starvation.

 

The Oiling System

I’ll do a short run through of the oil system in a combustion engine to give you a basic idea of what we are dealing with.

Firstly, oil lives in the sump pan. This is essentially a bucket of oil at the bottom of the engine which stores a supply of oil for the engine; this is directly under the rotating crank. Oil is sucked out of the sump by a crack driven pump and forced through an oil filter, which removes all the small particulates which might potentially cause damage upstream.

From the oil filter it feeds the main oil gallery which gives oil to the main bearings and crank, ensuring there is adequate lubrication and load support for the connecting rods. The main gallery also has a vertical feed going vertically towards the head. This lubricates the cam bearing surfaces and pressurizes the hydraulic lifters.

Oil slowly leaks out of the bearing surfaces, and flows back to the sump thanks to gravity. The restriction between the pump and atmosphere (the effective hole size in which the oil leaks out of) leads to a pressure build up in the oiling system. Once a given oil pressure is reached a blow-off valve allows oil to flow straight back into the sump, restricting how much oil pressure will be achieved. Therefore the less wear on an engine, the greater the restriction and the greater the running oil pressure (until the blow-off valve pressure, which is usually 60-70psi).

As an aside, when an engine is cold the oil is thick and viscous, and therefore the oil pressure is higher.

G13B Oil System

So, if for some reason the engine is starved of oil it will pump air and the oil density will drop, flowing easily through the gap in the bearings and reducing the oil pressure. Air does not lubricate or bear load very well, leading to excess wear and potential engine failure.

In short, oil pressure is an effective measure of engine health.

 

The Sump

So how does oil starvation occur? Well usually its one of three things, a lack of oil in the sump (check your dip-stick!), aerated oil or oil slosh away from the pickup. Keeping the sump full is easy, and really there is no excuse for having a low oil level, however the other two are not so obvious.

Oil aeration occurs when the crank stirs up the oil in the pan and fully/partially turns it into foam. This can be designed out with use of a Windage Tray; more on that later.

Oil slosh occurs due to the accelerations that are applied to the oil volume. If you achieve a lateral acceleration of 1g (at the apex of a corner for example), there will be a force pushing the oil against the side of the sump equal to gravity and it will set in triangular shape; as illustrated below:

Oil Slosh

In this case the pick-up is partially open to the air and pumps that as opposed to oil. This leads to bearing on bearing interaction, friction, wear and potential engine failure. The secret to good sump design is to reduce the chance of the pick-up being exposed to free air.

You can do this by using a tall deep sump, or by baffling and gating the sump. As the Locost is a small tightly packaged race car its nearly impossible to package a tall sump without running an impractically high ride height, so the sump needed to be baffled and gated, with an inbuilt windage tray.

 

Old/Poor Sump Design

My old sump was built from the flange of a standard front wheel drive sump, with custom sheet metal work underneath. The pickup was at the front and approximately central. It had longitudinal and lateral baffles with liberal drainage holes between each (making them almost useless) and a bolt in windage tray. It looked a whole lot like this:

Old Sump with Windage Tray

With the windage tray removed the baffles were accessible:

Old Sump Baffles

In hard right hand corners I think it was possible for the oil to slosh to the left hand side of the sump and expose the pick-up; as you can see there is no baffle in the central section where the pickup was located. The only saving grace of this design was its large capacity, giving minimal oil depth change when oil is trapped in the top end of the engine. Fortunately when I put slicks on the car it had terminal understeer and I don’t think I did any serious damage.

Given that the sump was off the engine, it was a great opportunity to inspect the oil/sump for particulates. The oil was clear of shiny aluminium bearing material, but there were some small bits of the cork gasket in the bottom; nothing scary but also suboptimal.

Blergh

I was happy to move on from this design…

 

New Sump Design

The new design was going to be wider and shorter than the original, positioning the pickup in the middle of four separate oil chambers, each giving the pickup instantaneous oil in the case of hard cornering. Also, the windage tray would bias towards the pickups central volume, to flood it and reduce the chance of oil starvation.

New Sump Flange

Fabrication started by cutting out the main flange to mount to the block. This was bolted to an old junk fitment engine I had lying around (I use this for making engine mounts, brackets etc).

New Sump

New Sump

New Sump Windage Tray

New Sump Pickup

Then the windage tray was cut to match the sump and measurements taken from the chassis.

New Sump Central Chamber

The sides of the sump were then cut and tacked to the windage tray. The central chamber around the pickup was mocked in place.

New Sump Gates

Sump Baffles

Welded Baffles

Then the baffles were put in place to create the four separate chambers. Four gates were added to the central chamber to avoid oil moving away from the central chamber in hard cornering; these were made from steel door hinges! Note that they have limiting tabs to stop the gates going over-centre and killing the engine. The baffles were welded into the bottom plate to stiffen the sump and ensure oil does not escape the central chamber.

Sump Drain

I almost forgot to add a sump drain plug (uh oh!), so I welded in an M12 nut. It turns out M12 course thread is not a standard sump plug size (arg!) so I had to use an M12 bolt with a magnet epoxied too it; could be worse.

Oil Leak Down Test

Once the whole thing was welded together it was tested for leaks using some old oil and left to sit for a few evenings.

Painted Sump

After this it got a snazzy coat of Racing Red!

Closing Comments

The sump is now bolted onto the car and we will see if it causes me any issues. On paper it should be a great improvement over my previous sump and I’m hoping it will give the confidence and peace of mind its designed too.

Before Christmas I will have gathered some track data, covering a large span of lateral/longitudinal accelerations and engine oil pressures. In a perfect world there would be no drop off in pressure over the full span of achieved accelerations; but realistically I’ll  be happy with just very low drop off and a healthy engine.

There is still plenty to do before hitting the track- front wheel arches, rear lights, blah, blah blah… I will get there eventually!

 

Fabrication: That time I made an Exhaust Manifold

I’m going to try to document a few of my older projects that fell through the cracks and didn’t make it on to here. Hopefully you’ll find these little articles both interesting and informative… and there are pictures!

A couple of years ago I made an exhaust manifold for a friends Seven. Having seen the stainless manifold on my Locost he wanted one in the same “over the chassis” style. The manifold on my Seven was/is OK, it does the job, but its not my best piece of work; I was learning along the way. The Locost itself is a testament to my abilities at each stage of its build; some parts are better than others due to improving my fabrication skills as I went along.

Locost Exhaust Manifold

Locost Exhaust Manifold 2

Locost Exhaust Manifold 3

Locost Exhaust Manifold 4

 

 

 

 

 

 

 

 

This second exhaust manifold project benefited from everything I had learn’t and was properly jigged and built close enough to equal length. I built it from separate bends of 316 Stainless Steel with 3/4inch headers and a 2 a inch collector. The primary lengths were specified based on the expanded volume of a single cylinder cylinder, going from atmospheric temperature to an exhaust combustion temperature I found on the internet (I have never measured exhaust gas temperatures before, so I think I can be forgiven for consulting the web).

From what I heard it did well on the dyno, and in truth I was sad to see it go; it took a lot of time and effort to make. Eventually the Locost will get one of the same quality, if not better.

Exhaust Manifold 1

Exhaust Manifold 2

Exhaust Manifold 3

Exhaust Manifold 4

3D Printer: Upgrades 2/3

It’s taken me almost two months to get around to writing part 2 of this series, opps! However this is because I have actually been using the printer, and working on a project for a friends rally car (watch this space).

Now where were we… ah yes, the heated bed. In the previous article I explained why a heated bed is a good upgrade for a 3D Printer, especially one that uses high temperature plastics such as ABS. Installing one is easy straightforward, however my little machine required a few modifications along the way.

To convert your printer to use a heated bed first you’re going to need, you guessed it, a heater to heat the bed.

1. Sourcing a Bed Heater

A simple flat Silicone Heated Bed. Easy to install... and ORANGE.

A simple flat Silicone Heated Bed. Easy to install… and ORANGE.

I chose to use a 12V Silicone Bed Heater. These are easy to get from China and come in an array of different sizes to suit your needs. As I write this, doing an ebay search brings up 47 of them from a range of manufacturers.

Truth be told I took this route because its what everyone else does, however there are some major benefits to this style of heater. Firstly they are simple to wire (4 wires, with feedback), they are relatively thin and they can be driven straight from most standard firmware.

 

Most common printer PCB’s have the ability to drive a 12 or 24 volt heated bed directly, however I opted to use an external power supply. My heater is rated at 350 watts, so at 12 volts it can draw up to 350/12 = 29.1 amps! I was not willing to push that through a thin PCB, no matter how much the manufacturer says its marginally spec’d to that ampage.

An all purpose 12v DC Power Supply. 240v to 12v made easy.

An all purpose 12v DC Power Supply. 240v AC to 12v DC made easy.

In hindsight I probably should have gone for a higher voltage heater and then wouldn’t have had to flow as many amps to achieve my desired bed temperature; especially given the fact my power supply has to drop down from 240 volts! A smaller step would have been more efficient. In fact 110V heated beds are available, their just less common.

 

 

2. Wiring the Heater

The heater has four wires, one pair is power/ground for the heater itself and the other pair are attached to a thermister embedded in the heater. The thermister wires were attached directly to the control PCB and this allowed the software to measure the temperature of the bed while printing. The power wires went to the external power supply via an automotive relay (12v 40amp). The relay was switched using the heated bed control off the PCB, which is usually used for driving the bed directly. This giving a lovely 12v output to charge the relay coil and switch on the bed.

Power Supply

IMG_20160525_190955

 

 

 

 

I ran the power switch and thermister lines through the case via some two pin connected. Initially I wired theconnectors straight to the aluminium printer chassis but soon realized one of the pins ground through the outer thread! This mean’t I had to print some little top hats to make sure the signals didn’t ground. Printing parts for the printer; it’s 2016.

Case ConnectorsExternal Connections

Working Temperature Feedback

 

 

 

 

Once this was all wired together surprisingly it worked straight away (well once the above earthing issues were fixed). This gave me closed loop temperature control of the bed, ensure a nice consistent temperature.

3. Fitting the bed

It wasn’t all straightforward. The Chinese manufacturer neglected to give any dimensions when listing the heater, so I had no idea how thick it was going to be. I had a feeling it was likely going to cause issues with the self leveling system, as this requires the bed to bottom out when being installed to get under the sensing probes.

Low and behold once I installed the heater the aluminium bed no longer fit. Fortunately I had my non-heated bed on hand and I used it to print taller probe mounts. Magic.

Raised Probe Towers

 

 

 

 

So that’s it for this installment. In part 3 i’ll go through building an enclosure and the tricks I’ve learn’t when printing ABS.

 

A closing thought and something to consider before getting one of these machines. The more I have used the printer, the more I have come to realize that it is as much a piece of workshop machinery as a lathe, mill or welder. It requires maintenance, care and cleaning to remain consistent and usable. In my experience, few people have the patients for this.

 

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